Studies of the effects of botulinum toxin injection in the treatment of oromandibular dystonia have included 18 patients thus far. Quantitative analyses of the effects on speech timing have been completed in 5 patients. Seven second repetitions of syllables, polysyllabic words, and sentences were completed. The durations of voicing for completion of each token were measured from acoustic oscillograms and found to be increased in the patients' pretreatment in comparison with the normal controls. Paired comparisons between pre- and post-treatment measures demonstrated significant decreases following botulinum toxin injection in word and sentence durations suggesting that intersyllabic pauses were decreased with treatment while speech articulation timing was not. Barium swallow studies are being conducted on a selected number of oromandibular dystonia patients before and after injection to determine whether the types of swallowing side effects can be predicted based on initial patient characteristics. The effects of fluency enhancing conditions (DAF, choral reading, white noise) on voicing interruptions during speech was examined in normal speakers. No significant changes were found that could not be accounted for by changes in speech rate. Three new studies in stuttering were initiated this year. We are conducting double blind cross-over studies of the effects of botulinum toxin on muscle activation abnormalities. Also we are comparing the effects of laryngeal muscle injections with lip or jaw injections in stutterers. A double blind cross-over study comparing the effects of chlomipramine and desmipramine on stuttering is being conducted in collaboration with the Child Psychiatry Branch, NIMH.